Carrier arrangement and smart card comprising overvoltage protection device.
Electrostatic voltages arise whenever the number of positive charge carriers in a body does not match the number of negative charge carriers. If the voltage difference is large enough, then an electric current pulse can flow between two bodies even via a normally electrically insulating material. This is referred to as an electrostatic discharge. Electrostatic voltages and electrostatic discharges, due to the high electric field strengths and current pulses associated with them, can lead to the destruction of electrical components. Particularly in integrated circuits, electrostatic discharge constitutes one of the commonest causes of failure since the insulators used therein, such as silicon dioxide, for example, can easily be damaged on account of their small dimensions. In smart card modules, security controllers have to be protected against electrostatic discharge according to ISO standards.
In order to afford protection against electrostatic overvoltages and discharges, it is possible to overdimension electrical components in the smart card modules or carrier arrangements to increase their dielectric and breakdown strength.
Spark gap arrangements are another type of overvoltage protection. Such an arrangement between, for example, contacts for which an overvoltage is intended to be avoided, enables a controlled electrostatic discharge. In this case, the spark gap arrangement is configured in such a way that the spark discharge takes place at e.g. lower voltages in the spark gap arrangement, than at other locations of the smart card module. During the discharge, therefore, the current pulse flows through the spark gap arrangement and not through sensitive electrical components. The use of a spark gap arrangement for smart card modules is virtually free of perturbing reactions, simple in terms of construction and multiply usable. Furthermore, a spark gap arrangement does not consume any additional current consumption and obviates the need for overdimensioning of components.